Blade sharpener

ABSTRACT

A blade sharpener ( 10 ) comprises sharpening strip providing carriers ( 12 ) and ( 14 ) each including an obliquely extending linear sharpening strip providing rod ( 16 ) and carrier movement non-interference guiding means in the form of a slot defining formation formed by facing rail pairs ( 18 ), ( 20 ) facing one another across a slot ( 22 ). The rail pairs ( 18 ) and ( 20 ) form part of a carrier support frame ( 24 ) to which the carriers ( 12 ), ( 14 ) are mounted to be displaced in diametrically opposed directions and along the spacings formed between the rails of the rail pairs ( 18 ), ( 20 ). A crossover point ( 28 ) is defined between the rods ( 16 ) within which the cutting edge of the blade of a knife is in an abrasion fashion moved during a sharpening action. The crossover point ( 28 ) is constrained to move along a linear sharpening path extending along the slot ( 22 ) during sharpener use. The carriers ( 12 ), ( 14 ) are biased by springs ( 26 ) to cause the return of the crossover point ( 28 ) to an inter strip commencement crossover position.

BACKGROUND TO THE INVENTION

The manual sharpening of blades is a common actively. This can beachieved in a variety of ways including by way of the manual cyclicalreciprocation of a blade in a notch or forked formation defined betweensharpening elements. While such technique of sharpening is well knownthe precision sharpening of a blade is an often-desired activity amongstknife specialists. In this regard the maintenance of the primary edgeunderscoring faces of a blade ending in its cutting edge at a fixedangle during a sharpening routine is of primary importance. It is anobject of this invention to address this requirement. While ofparticular use for sharpening the blades of knives the invention is notlimited thereto but can be applied for sharpening any relevant type ofblade.

1. Field of the Invention

This invention relates to a manually operable blade sharpener at leastemployable for the precision sharpening of a blade. Although not solimited the sharpener of the invention finds useful application in thefield of the sharpening of knife blades.

2. Prior Art Description

Equipment for the manual sharpening of blades by way of the manualcyclical reciprocation of a blade in a notch or forked formation definedbetween sharpening elements is known in the art. U.S. Pat. Nos.4,550,632 and 5,440,953 both define sharpening elements crossing oneanother in defining a sharpening notch. Both patents also presentguiding means for guiding a blade into a sharpening notch. None of thethese patents, however, address the situation of precision sharpening astheir sharpening elements are swivellably mounted to a base that thusgives rise to a continuously changing sharpening angle in theperformance of a sharpening routine. While the subject matter of U.S.Pat. No. 4,624,079 discloses sharpening elements that are mounted tomaintain a fixed sharpening angle it does not present a guide pathassociated therewith. It also thus does not provide for the precisionsharpening of a blade.

BRIEF DESCRIPTION OF THE DRAWING

The invention is now described, by way of example, with reference to theaccompanying drawings. In the drawings

FIG. 1 shows a manually usable blade sharpener in the form of a knifeblade sharpener, in side elevation,

FIG. 2 shows the blade sharpener of FIG. 1 though with a modification asregards the ability to alter the slope of a blade-sharpening pathdefined along the sharpener,

FIG. 3 shows the sharpener of both FIGS. 1 and 2 in end elevation,

FIG. 4 shows the sharpener of the FIG. 1 in plan view,

FIG. 5 stepwise shows the operation of the sharpener though omitting themodification as regards the ability to alter the slope of the bladesharpening path, and

FIG. 6 shows in detail the operation of the sharpener as modified toalso alter the slope of the blade-sharpening path.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIGS. 1 to 5 of the drawings a blade sharpener in the formof a knife blade sharpener is generally indicated by reference numeral10.

The sharpener 10 comprises two horizontally displaceably mountedsharpening strip providing carriers 12 and 14 respectively, eachincluding an obliquely extending linear sharpening strip providing rod16 and carrier movement non-interference guiding means in the form of aslot defining formation as providing a slot defining frame member layoutformed by facing rail pairs 18, 20 facing one another across a slot 22.The rail pairs 18 and 20 form part of a carrier support frame 24 towhich the carriers 12, 14 are mounted to be displaced in diametricallyopposed directions once the sharpener 10 is used for blade sharpeningpurposes. The carrier 12 is thus mounted to be outwardly displaced inthe direction of arrow 13 and the carrier 14 in the direction of arrow15. The carriers 12, 14, as mounted in snug adjacent displacingrelationship relative to one another, are mounted to be displaced alongthe spacings 26 formed between the rails 18.1, 18.2 and 20.1, 20.2 ofthe rail pairs 18, 20.

While the carriers 12, 14 are freely displaceably mounted theirrespective ranges of displacement are limited to cause the rods 16 tomaintain a forked crossover relationship by forming a randomlydisplaceable crossover point 28 defining a cutting angle 17 within whichthe cutting edge of the blade of a knife is in an abrasion incurring waymoved during a sharpening action. The location of the crossover point 28is naturally dependent on the relative positioning of the carriers 12,14 and thus the rods 16 but is limited to a uni-planar displacement in aplane parallel to the planes of displacement of the carriers 12, 14.While the crossover point 28 is randomly displaceable within therelative operative ranges of the carriers 12, 14, it is naturallyconstrained to move along a linear sharpening path extending along theslot 22 once the sharpener 10 is used for performing a blade sharpeningaction, as more fully discussed below.

The carriers 12, 14 are limited to their ranges of displacement by wayof limiting means in the form of adjustable stops that are provided, asregards outward displacement, by stop screws 30 adjustably fittingthough threaded apertures in the end sections 24.1 of the frame 24 thatconstrains outward displacement by coming to abut against frame members12.3, 14.3 respectively. As regards inward displacement the limitingmeans is provided by nuts 32 fitting adjustably onto threaded ends ofupper sliding arms 12.1, 14.1 forming part of the respective carriers12, 14. To cause the return of the crossover point 28 to an inter-stripcommencement crossover position in the region of the entrance to theslot 22 when not exposed to a sharpening action, the carriers 12, 14 arebiased by biasing means in the form of springs 36 each extending betweenthe appropriate end section 24.1 of the support frame 24 and a hookformation 23 formed on the relevant carrier 12, 14. To cushion inwarddisplacement of the towards the nuts 32 as urged by the springs 36 whena blade is rapidly removed from the slot 22 the arms 12.1, 14.1 arefitted with cushioning springs 27. Although not shown the tensioning ofthe springs 36 can be adjustable by either replacement of springs ofdifferent tension or by providing a series of hook formations 23 foreach spring.

The leading side surfaces 16.1 of the rods 16 are naturally abrasivelyformed for performing their combined abrasive sharpening effect once thesharpener 10 is in use.

The support frame 24 is constituted from its ends frame sections 24.1and overhead sections 24.2 running into rail pair securing formations 25or adjustment means as shown in FIG. 2 for the modified sharpener 10 anddiscussed in more detail further on. The rail pairs 18, 20 in turn runfrom the formations 25 into a stand section 24.3 via which the frame 24is anchored to a base 38 forming part of the sharpener 10. The railpairs 18, 20 flare outward at the inlet 34 to the slot 22 to facilitatelocation of a blade into the slot 22.

The carriers 12, 14 are displaceably mounted to the support frame 24 viatheir upper sliding arms 12.1, 14.1 that pass slidably along apertureseach formed at a high elevation through aperture blocks 42 forming partof the end sections 24.1 and lower sliding arms 12.2, 14.2 eachsupported at both ends in apertures 44 formed in aperture blocks 46 alsoforming part of the end sections 24.1. Each of the upper sliding arms12.1, 14.1 is only supported in the end section side towards which itslides on the carriers 12, 14 being caused to slide more out of overlapwith respect to one another.

To accommodate a variety of primary edge blade angles the carriers 12,14 make provision for adjustment of the slopes of the rods 16 and thusof their sharpening surfaces 16.1. This is achieved by having the rods16 swivellably mounted at their upper ends 16.2 to rod support carrierframe sections 48 while the lower end 16.3 of each rod 16 is releasablysecurable to one of a series of rod lower end positions of securing inthe form of rod connecting apertures 50 that are suitably arcuatelyarranged to permit the registration and securing of a selected one ofthe apertures 50 with an aperture formed at the lower end of the rod 16.The apertures 50 are presented along aperture carriers 52 integrallyformed above the lower sliding arms 12.2, 14.2.

As shown in FIG. 5 the use of the sharpener 10 involves conventionallycyclically reciprocatingly moving the blade of a knife along theblade-sharpening path that extends down the slot 22. As the object ofthe sharpener 10 is to achieve precision sharpening of the cutting edgeof a blade, the path does not necessarily extend centrally down the slot22.

A typical blade for which the sharpener 10 is useful in performing aprecision sharpening action comprises primary edge underscoring facesending in its cutting edge. Trailingly as regards the width of the bladethe next part of the side faces of a blade is found in the secondaryfaces that in turn lead onto the broad trailing side faces. The typicalblade is normally symmetrically formed with precision sharpening of theblade with the sharpener 10 thus involving the primary edge underscoringfaces.

Such precision sharpening involves maintaining the position of theprimary edge angle underscoring faces 54 of a blade 56, as shown in thedetail to FIG. 5(a), and as terminating in the cutting edge 58 of theblade 56, in a fixed and preferably symmetrical relationship withrespect to the crossover point 28 throughout a cyclical andreciprocating blade sharpening action. This is achieved by maintainingthe central plane through the blade 56 and consequently its broad sideface areas 60, as trailing the secondary faces 63 in parallel with thecentral axis 62 down the slot 22. When the width of the blade 56, asdefined between opposite face 60, is such that a snug but freedisplacement of the blade 56 along the slot can be achieved, theblade-sharpening path is naturally defined down the slot 22 as such.Cyclical to-and-fro reciprocation of the blade 56 along the slot 22 hasthe effect of maintaining the blade 56 in parallel with the axis 62 downthe slot 22 in turn causing its primary edge angle underscoring faces 54to maintain a fixed relationship relative to the crossover point 28.

When the blade width is however less than the width of the slot 22 thesharpening path is defined down one of the rail pairs 18, 20 in that theblade 56 is maintained against the appropriate rail pair 18, 20 duringthe sharpening action. This scenario is typically shown in FIG. 5. Amanually applied cyclical reciprocating sharpening action has the effectof causing the blade 56 to move up and down the sharpening path and toand fro in the crossover point 28 according to FIGS. 5(a) to 5(b) withthe crossover point 28 following the cutting edge 58 of the blade 56owing to the biasing effect of the springs 36. As the crossover point 28is freely uniplanary displaceable it automatically finds its position ofblade sharpening edge bedding when the blade 56 is moved along itssharpening path.

A typical sharpening routine involves as first step the desirablesetting of the slopes of the rods 16 and thus of their surfaces 16.1 asdescribed above.

While blades are often constructed as explained above, other forms ofblade design are also found. In again referring to FIG. 2 and also toFIG. 6 the modified sharpener also accommodates blades of which thebroad side face areas do not extend in parallel with one another.Typically such broad side face areas run directly into their primaryfaces. Otherwise such blades may have secondary faces while the primaryfaces still extend in a non-parallel relationship with one another. Tostill achieve the desired sharpening action for such blades inmaintaining their primary edge underscoring faces, as ending in theircutting edge, in the crossover point 28 during use of the sharper,provision is made for adjusting the slope of at least one of the railpairs 18, 20. This is achieved by having the appropriate rail pair 18,20 swivellably mounted in its root as found in its point of connectionto the stand section 24.3, as shown in FIG. 2, while its remote end isadjustably secured to the overhead section 24.2 by way of an adjustmentfacility (not shown in detail) including locking means enabling there-lockable adjustment of the slope of the appropriate rail pair 18, 20.As shown in FIG. 2 the position of adjustable locking to the overheadsection 24.2 provides an indicating scale 64 for indicating the extentof adjustment of the rail pair 18, 20 relative to the vertical.

Use of the FIG. 2 embodiment of the sharpener 10 in conjunction with ablade 64 of which the broad side areas are not parallel to one anotherinvolves desirably pre-setting of the slope of the relevant rail pair18, 20 to the effect of ensuring that the centre line 66 of such blade64, as shown in FIG. 6(a), is parallel to the vertical. The sharpeningpath is in this case defined along the rail pair 18, 20 of which theslope is suitably adjusted. This has the effect that the primary edgeunderscoring faces 68 still symmetrically fit the crossover point 28, asshown in more detail in FIG. 6(b).

A sharpening routine performed with the modified sharpener 10 of FIG. 2of which the rail pair slope is appropriately adjusted can thus beperformed with the same extent of precision, as is the case for a bladeof which the broad side areas are parallel to one another, as discussedwith reference to FIG. 5. As shown in FIGS. 6(c) and 6(d) the modifiedsharpener 10 can naturally also be used for blades having parallel broadside face areas. In such case the adjustable rail pair 18, 20 is simplyadjusted to cause the rail pairs 18, 20 to extend parallel to oneanother thus effectively having a sharpener similar to that shown inFIGS. 1 an 5. As a blade used in conjunction with the FIGS. 6(c) and6(d) embodiment is the same as that used in the FIGS. 1 and 5 embodimentit carries the same nomenclature.

Once a blade has been sharpened by means of the sharpening rods 16 thefinal step in its preparation is often its steeling. This is normallydone at a blade cutting edge underscoring angle of larger that the angleof sharpening. If this step is required the sharpener 10 can simply bearranged to enable replacement of the rods 16 by steeling rods (notshown in detail but implied by the FIG. 2 embodiment of the invention).Alternatively while not shown the sharpener 10 can include steeling rodsfitted with appropriately arranged clips that automatically define thedesired increased underscoring angle once clipped to the rods 16.

1. A manually usable blade sharpener at least employable for theprecision sharpening of a blade comprising at least two sharpening stripproviding carriers (12, 14) mounted to be independently linearly andalso in a to-and-fro snug sharpening strip contiguously formed crossoverrelationship displaced along parallel planes with respect to oneanother, each carrier (12, 14) thus in such a way formed with a linearlyextending abrasive sharpening strip (16.1) to cause the strips (16.1),as extending in a sharpening blade accessible forked crossoverrelationship relative to one another, to form a crossover point (28)that is randomly though in a common plane displaceable in conjunctionwith displacement of the carriers (12, 14), as biased by biasing means(36) to an inter-strip commencement crossover point defined at the oneend of the range of displacement of the carriers (12, 14) relative toone another and as each limited by limiting means (30, 32) to bedisplaced within an operative range, with an acute sharpening angle (17)of fixed magnitude being formed at the crossover point (28), and carriermovement non-interference guiding means (18,20) presenting a linear pathof blade traversal characterised by the guiding means (18,20) definingin association with a linear route of crossover point displacement, asassociated with appropriate displacement of the carriers (12, 14) and inturn brought about by the manually controlled displacement of a bladealong the path of blade traversal once the sharpener (10) is in use, ablade sharpening path that extends from a point of blade insertion (34)associated with the inter-strip commencement crossover point, to alocation associated with the end of the range of displacement of thecarriers (12, 14) remote from the inter-strip commencement crossoverpoint defining location, the primary edge angle underscoring faces of ablade of which the primary edge angle is intended to be sharpenedaccording to the sharpening angle (17) of the sharpener and at theslopes of the sharpening strips (16.1) by way of a conventionallyreciprocating and manually performed cyclically sharpening action ofsuch blade in the blade sharpening path, thus resulting in the linearand constant sharpening angle to-and-fro movement of the crossover point(28) along the path of blade traversal while causing the precisionsharpening of such blade.
 2. A blade sharpener as claimed in claim 1 inwhich the carriers (12, 14) are mounted to be horizontally displacedonce the sharpener (10) is in its use condition thus being displaceablein diametrically opposed directions during use of the sharpener (10). 3.A blade sharpener as claimed in claim 2 in which the limiting means (30,32) that is involved in limiting the range of displacement of thecarriers (12, 14) is in the form of adjustable stops that, one on theone hand, limit the extent of travel of the carriers (12, 14) in theiroutward and thus crossover point descent direction and, on the otherhand, their extent of travel in their crossover point ascent directionof travel relative to one another into which latter direction of travelthe carriers (12, 14) are biased by the biasing means (36).
 4. A bladesharpener as claimed in claim 2 in which at least one of the carriers(12, 14) is arranged to enable the at least stepwise adjustment of theslope of its sharpening strip (16.1).
 5. A blade sharpener as claimed inclaim 2 in which the carriers (12, 14) are in the form of carrier frameseach formed with a sharpening strip presenting rod (16) appropriatelypresenting its sharpening strip (16.1), adjustment of the slope of theappropriate sharpening strip (16.1), if not for both carriers (12, 14),where the carriers are so disposed, thus involving the adjusbT1ent ofthe slope of the relevant sharpening strip presenting rod (16).
 6. Ablade sharpener as claimed in claim 5 in which adjustment of the slopeof the adjustable sharpening strip presenting rod (16), if not both rodsand thus for each rod (16), is achieved owing to the rod (16) beingswivellably mounted to the remainder of its carrier frame (12, 14) at anoverhead position (16.2) while being securable at its remote end to theselected one of a series of suitably arcuately arranged rod lower endpositions of securing (50) as forming part of the carrier frame.
 7. Ablade sharpener as claimed in claim 2 that is arranged to cause the pathof blade traversal to at least extend at least substantially verticalonce the sharpener is operatively positioned.
 8. A blade sharpener asclaimed in claim 7 in which the guiding means (18, 20) is in the form aslot defining formation as opened at one end and which end forms theoverhead position of entry into a slot (22), as thus defined by theformation, once the sharpener is operatively positioned with theposition of entry consequently being associated with the inter-stripcommencement crossover point while the blade sharpening path extendsalong at least one of the sides of the slot (22), against which side oneof the side faces of a blade is urged during the performance of asharpening action for maintaining it at a constant slope relative to thesharpening angle of the sharpener trough in the case of a snug blade fitdown the slot in at least which case the slot defining formation extendsalong a uniform width, the path being defined along the slot as such,the sharpener also being employable for less precise sharpening of anon-snug-fitting blade by a way of conventional cyclical to and fromovement in the slot without necessarily urging one of its side facesagainst one of the sides” of the slot.
 9. A blade sharpener as claimedin claim 8 in which the slot defining formation forms part of a carriersupport frame (24) as displaceably mounting the carriers (12, 14), thesupport frame consequently including the slot defining formation in theform of a slot defining frame member layout that is shaped to present anoverhead entrance to the slot that promotes the ease of location of ablade intended to be sharpened towards the blade sharpening path.
 10. Ablade sharpener as claimed in claim 9 in which the slot defining framemember layout is in the form of facing rail pairs of which each pairdefines the side of the slot (22) with the rail pairs facing one anotheracross the slot while being formed with progressively flaring upper endsto accommodate blade entry into the slot (22), the carriers (12, 14)being mounted to the carrier support frame (24) to result in their beingdisplaceable between the rails of the rail pairs resulting in the bladesharpening path being defined in the intermediate zone found between thevarious rails of the rail pairs.
 11. A blade sharpener as claimed inclaim 10 in which the carriers are each mounted to the support framebyway of an upper and lower sliding arm (12.1, 12.2, 14.1, 14.2) ofwhich the lower sliding arm (12.2, 14.2) serving as carrier base, snuglyslidably engages with apertures in opposite ends of the support frame(24) while the upper sliding aim (12.1, 14.1) engages with an aperturein the end of the frame (24) towards which the relevant carrier isdisplaced on crossover point descent as perceived with the sharpener aspositioned for use.
 12. A blade sharpener as claimed in claim 8 in whichthe slot defining formation makes provision for adjusting the slope ofat least one of its slot defining sides in a way that gives rise to aslot entry broadening action for accommodating the precision sharpeningof a blade of which the side faces do not lie in parallel with oneanother; adjustability in the case of the slot defining formation beingformed by the slot defining frame member layout being provided for bythe part of the layout that forms at least one of the sides of the slotbeing swivellably mounted in its root to a lower location on thestationary part of the carrier support frame for re-lockably alteringthe slope of this part of the layout by way of locking means situatedremote from its root position that is arranged to enable its releasableand adjustable locking to an overhead section of the stationary part ofthe carrier support frame.
 13. A blade sharpener as claimed in claim 12that includes an indicating scale (64) for indicating the extent ofadjustment of the slope of the adjustable slot defining side of the slotdefining formation, when formed by a slot defining frame member layoutof which the one side is swivelably mounted in its root the indicatingscale thus being presented in conjunction with the locking means.